The present invention relates to a duplex copying machine, and more specifically to a duplex copying machine having an auto document feeder, which is capable of making one or more sets of duplex copies automatically in the case of sheet type originals regardless of the types of originals to be reproduced, such as originals having images on one side, originals having images on both sides and the combinations of the aforementioned two types.
The conventional method of making a duplex copy comprises the following steps. An original is placed on a duplex copying machine and an image of the original is formed on the first side of a copy sheet by conventional techniques, and after the original is turned over or it is replaced with another original, another image is likewise formed on the second side of the copy sheet. This is not always speedy.
Recently, particularly with respect to sheet type originals, there is a great demand for increasing the duplex copying speeds although there are various kinds of originals in the sheet type originals, such as an original having images on one side, an original having images on both sides and their combinations. Furthermore, in the case of the sheet type originals, when a large number of duplex copies are made, it is critical how to make copies in the order of the pages speedily, without necessitating the resetting of copies afterwards.